How to know when battery has completed charging if tablet is off?

I have had the TPT for a few days now, but I can't seem to find how to determine if the battery has finished charging if the tablet is off. When I plug in the charge cable an icon appears to indicate it is charging, but after that there is no other indication that the tablet is charging (save for it getting warm of course) Is it possible to know when the battery has completed charging without turning the tablet on?

- Tablet on but with screen off. While charging red LED is on constantly.

(a few minutes later, the LED is off. It was at 92% charge. Checking... It is still at 92% charge)

- Tablet fully off. Connect USB power. Screen comes on showing battery icon then goes off. Red LED doesn't come on at any point during this. Unless the LED comes on when it fully charges, there is going to be no way to read the state of the TPT's charge whether it is in sleep mode or fully tunred off.

So, at the moment, the red LED doesn't do anything useful.

It does seem clear to me that while charging, the LED should be flashing (implying activity or a changing state). When fully charged but still plugged in, the LED should be on continuously. I don't know what profile would be best when taken off the charger. Maybe solid red when mostly charged, slow flashing when the battery level drops to 30% or so, then a faster flashing at lower charges... I think it is just not working at all the way it is now.